Method of and apparatus for conducting catalytic reactions



Patented Aug. 17, 1937 PATENT OFFICE DIETHOD OF AND APPARATUS FOR CON-DUCTING CATALYTIC REACTIONS Henry F. Merriam, was Orange, N. 1..

to General Chemical Company,

alsignor New York,

N. Y., a corporation of New York Application July 23, 1932,. Serial No.624,179

12 Claim.

This invention relates generally to a method of and apparatus forconducting catalytic reactions, more particularly the reduction ofsulfur dioxide to sulfur and/or hydrogen sulfide. The inventioncontemplates chiefly the reduction of sulfur dioxide to elemental sulfurand accordingly, for convenience, the invention is herein described inconnection with the production of elemental sulfur, although it is to beunderstood that the principles of the present improvements apply to theformation of hydrogen sulfide if such end product is desired.

More particularly, the invention relates to a process for the productionof elemental sulfur from sulfur dioxide or gas mixtures containing thesame. In the more limited aspects, the invention is directed to theproduction of sulfur from relatively concentrated sulfur dioxide gasmixtures such as may be obtained, for example, by

decomposition of sulfuric acid sludges comprising waste products of oilrefining processes. The invention further contemplates the reduction ofcomparatively concentrated sulfur dioxide gas mixtures in a reducingreaction involving the use of finely divided catalytic materials such asbauxite fines.

It has heretofore beenproposed to reduce sulfur dioxide to sulfur bypassing a gas mixture containing reacting proportions of sulfur dioxideand reducing agent over catalysts such as bauxite. The reduction ofsulfur dioxide to elemental sulfur by means of'reducing agents takesplace in an exothermic reaction in which relatively large quantities ofheat are generated. In such reactions, when the temperature risesexcessively,

hydrogen sulfide tends to form, thus reducing the Y amount of sulfurrecovered as such. Accordingly,

when elemental sulfur is the desired end product.

the reaction is preferably carried out at lower 40 temperatures.

In prior methods, the sulfur dioxide concentration of the gas stream hasbeen comparatively low, and correspondingly small amounts of heat areevolved. Hence, it has been possible to carry out the reduction processby passing the reacting gas mixture through bedsof relatively closelypacked catalytic material since the small quantitles of waste heatgenerated give rise to no particular difficulties in controlling thetemperature of the reaction. However, when operating with concentratedsulfur dioxide gas mixtures, large quantities of heat are evolved, andin order to recover maximum amounts of sulfur and reduce the formationof hydrogen sulfideto a minimum, 56 adequate temperature control of theprocess is One of the principal objects of the invention lies in theprovision of a process by which elemental sulfur may be economicallyproduced by reduction of the sulfur dioxide content of a concentratedsulfur dioxide gas mixture. A further object of the invention comprisesthe provision of a method whereby large volumes of reacting gases may bepassed through a reaction chamber or converter and effectively contactedwith catalytic material therein without creating high resistance to gasflow through the converter. The invention also contemplates a method bywhich catalytic material in finely divided form may be advantageouslyemployed, and further comprises the provision of apparatus by which theimproved process may be carried out.

According to one preferred embodiment of the invention, elemental sulfuris produced from a relatively concentrated sulfur dioxide gas, such asmay be obtained by the decomposition of acid sludges, by mixing with thesulfur dioxide gas a gaseous reducing agent, and amounts of inert gasesin quantities to dilute the reactant gas mixture to such extent that thetemperature of the subsequent reduction reaction, carried out in thepresence of a catalyst, may be controlled and maintained withinhereinafter specified optimum limits. This dilution of the sulfurdioxide gas involves generally, a comparatively large increase in volumeof the gas mixture. According to the invention, the reactionof sulfurdioxide andreducing agent may be effectively carried out,notwithstanding the large increase in gas volume, by passing the gasstream through a catalyst body comprising a plurality of. suspendedmounds of loosely associated, finely divided catalytic material. Thecatalyst body in the converter, maintained in such condition throughoutthe reaction, includes a large number of relatively wide, unobstructedcircuitous gas passages whereby efiicient contacting of reactant gasesand catalyst is effected, and resistance to fiow of large volumes of gasthrough the catalytic body is minimized.

A further appreciation of the objects and advantages of the inventionmay be had from a consideration of the following description taken inconnection with the accompanying drawing in 5 which,--

Fig. 1 is an elevation, partly'in section, of one form of apparatus inwhich the process constituting the invention may be carried out,

Fig. 2 is a perspective showing the arrangement of the baflles in thereaction chamber, and

Fig. 3 indicates diagrammatically an acid sludge decomposing unit.

Referring to the drawing, the reference numeral I0 indicates a convertercomprising preferably a cylindrical steel shell having therein afirebrick lining l2. The lower end of the converter is funnel-shaped,and communicates through an opening l3 with an outlet chamber l4 adaptedto receive catalytic material being discharged from the converter.Passage of material through opening I3 is controlled by a slide valvel5. Catalytic material may be withdrawn from the chamber I through anoutlet conduit l6, likewise controlled by a slide valve l1. It

will be apparent that catalyst may be discharged from the converterwithout admitting air thereto.

At the lower end of the reaction chamber is a firebrick arch 20supporting a plurality of baffles 2| constituting checkerwork indicatedgenerally by the reference numeral 22. One feature of the inventioncomprises the particular construction.

and arrangement of the checkerwork in the reaction chamber so as toafford intimate contact of the reactant gases, and to reduce to aminimum resistance to flow of the-gas stream through the converter.Checkerwork 22 comprises a plural- I ity of superposed layers or series23, each series including a plurality of horizontally disposed,elongated baffles 2|. The ,baflles 2|, of each series 23, are preferablymade of bauxite brick and are arranged parallel to each other and spacedapart a distance somewhat less than the width of an individual bafile23. The battles of each series contact with and are disposed pref= 5erably at right angles with respect to the baiiles of immediatelyadjacent upper and lower series. As will be seen from an inspection ofFig. 2, the battles of alternate series are parallel, but alternateseries are offset horizontally so that there are no vertical channels ofappreciable length in the checkerwork. Accordingly, the gas passagesthrough the checkerwork are circuitous, and catalytic material on thebafiles presents a large surface to the gas stream flowing through the 5converter.

Finely divided catalytic material may be fed into the upper end of theconverter through a feed mechanism 30, terminatingat the lower end in aninlet conduit 3| projecting into the reaction 30 chamber. The chargingchamber 32 of the feed mechanism is provided with an inlet valve, 34operated by a lever 35 pi'vot-ed at 36. Flow of material from thechamber 32 into the conduit 3| is controlled by a similar valve 40 onthe lower end 5 of a rod 4| passing axially through the valve 34, valve43 being operated by a lever 44 pivoted at 45. Immediately beneath thelower end of the inlet conduit 3| is a cone 46 adapted to distribute thecatalytic material evenly over the upper sur- 70 face of the checkerwork22.

Reacting gases are charged into the converter through a conduit 50connected at one end to theoutlet side of blower 5| and at the other endwith an enlarged sleeve 52, surrounding inlet pipe 3|, 75 and openinginto the reaction chamber. The inlet side of the blower isconnectedthrough pipes 33 and 33 with a source of gas supply. Reducinggases may be drawn into the pipe 56' through a connection 51 havingtherein a control valve 58. Gaseous products of reaction are dischargedfrom the converter through an outlet pipe leading to'suitable condensingapparatus. Any desired quantities of reacted gases may be withdrawn fromthe lower end of the converter, by the blower 5|, through a conduit 3|,controlled by valve 62, and opening at'one end into the converter and atthe other end into the pipe 55 on the inlet side of the blower.

Since the invention has particular application to the production ofelemental sulfur from concentrated sulfur dioxide gas mixtures, thefollowing illustrative example is given in connection with the recoveryof sulfur from acid sludges.

Sulfuric acid sludges resulting from the refining of oils vary widely incomposition, one representative sludge containing 45% sulfuric acid, 35%water, and 18% hydrocarbons. Although the invention is, of course, notdependent upon any particular method for the production of aconcentrated sulfur dioxide gas mixture or process for the destructivedistillation of acid sludge to produce a concentrated sulfur dioxide gasmixture, decomposition of the sludge may be advantageously efiected byexternally heating a charge of sludge, in a substantially air-tightretort, such as Fig. 3 of the drawing, at relatively low temperatures,for example from 150- 325 C. On heating, the sulfuric acid contained inthe sludge is reduced by hydrogen of hydrocarbons and/or by thecarbonaceous matter present in the sludge, and the gas mixture evolvedand discharged from the retort through line 65 contains sulfur dioxideand water as the majorconstltuents, together with smaller quantities ofhydrocarbon vapors, carbon dioxide, carbon monoxide and oxygen.

The exit gases from the acid sludge decomposition apparatus may becooled to say. 40 C., in

a cooler 63 of any suitable type and the bulk of l the water andhydrocarbon vapors are condensed, separated from the gas stream, anddischarged through line 63. Since decomposition of the sludge ispreferably effected substantially in the absence of air or otherdiluting gas, after separation of water and condensable hydrocarbons,the retort gas mixture in line 10 is rich in sulfur dioxide and maycontain, for example by volume, 91% sulfur dioxide, 2% water and 7%carbon dioxide.

A gas mixture of such composition is drawn into the apparatus throughinlet pipe 56 by blower 5|. The valve 53 in pipe 51 is opened to permitadmission to the system of reducing agent,

' for example, natural gas so as to provide in the resulting gas mixturean excess of reducing gases,

mately by volume 61% 80:, 33% CH4, 5% CO2 and the balance water vapor.

A supply of catalytic material, such as bauxite fines, is maintained inthe chamber 32 of the feed mechanism. Before reacting gases are admittedto the converter, the valve 40 is opened to permit admission to theconverter of sufficient catalytic material to form on the top of each ofthe baiiles small mounds of loosely associated catalytic material, anyexcess falling through the openings in the arch 20 and into thefunnelshaped bottom of the shell. The gas mixture containing sulfurdioxide and reducing agent is checkerwork 22. Because of the particulararrangement of the baiiles comprising the checkerwork, there areprovided numerous relatively large unobstructed gas passages through theconverter. At the same time, the bailing effect of the checkerwork issuch as to cause repeated contacts of reacting gases with the largesurfaces, of catalytic material on the bailles. Be-

cause of the relatively rapid movement of the gas stream through theconverter and the comparatively finely divided nature of the catalyticmaterial. the latter may tend to drop gradually, though at a relativelylow rate, through the reaction chamber, co-current with the flow of thegas stream. 'I'he catalytic material passing through arch is collectedin the lower end of the shell, and may be withdrawn from the ap- 20paratus, without permitting the admission of air to the converter, andreturned to charging chamber 32 by any satisfactory mechanism. Duringoperation, the inlet valve 40 may be opened from time to time asrequired to feed into the converter amounts of catalytic materialcorresponding to those withdrawn from discharge chamber ll. However,after operation is under way, but little replacement of catalyticmaterial is required.

Reduction of the sulfur dioxide to elemental sulfur in the presence of abauxite catalyst may be effected at elevated temperatures generallyabove 425 C. When the operation of the present process is initiated, theincoming gases are preheated by any appropriate means, preferably toabout 425-475 Cl, and introduced at this temperature into the reactionchamber. The reduction reaction taking place in the converter isexothermic, and particularly where the concen- 40 tration of sulfurdioxide is high, large quantities of heat are generated. If thetemperature is per- .mitted to rise about, say, 650 C., relatively largequantities of hydrogen sulfide tend to form. Hence, where it is desiredto produce elemental 4,5 sulfur, the temperature in the reaction chambershould preferably be so controlled as to avoid temperatures at theoutlet end of the converter substantially in excess of about 650 C.

Temperature control of the reaction may be had in various ways, althoughin accordance with the present method, it is preferred to withdrawregulated quantities of reacted gases-from the lower end of theconverter, and mix the same with the incoming gas stream, thus dilutingthe latter with reaction products which are largely inert with respectto the reaction. Accordingly, valve 62 in the pipe 6| is opened topermit withdrawal by blower Il from the converter of sufflcientquantities of reacted gases to dilute the 5 gas mixture passing throughthe pipe 50 into the converter to such extent as to avoid excessivetemperatures in the converter. Since in the present example, theconcentrated sulfur dioxide gas mixture entering the inlet pipe 56 is attemperatures of about 40 C., the admixture of hot reacted gases from theconverter with the incoming gas stream serves a twofold purpose, and inaddition to diluting the incoming gas stream to the desired degree,preheats the same so that the temperature .of the gas mixture enteringthe upper end of the converter is about 425-475 C. It will be understoodof course, that the quantity of reacted gases withdrawn from theconverter through pipe connection 0|, admixed with the incoming gasstream and recycled through the converter is dependent upon theparticular operating conditions arising. For example, where the gas inconduit 58, after admission of reducing gas through inlet 51, isconstituted as above noted, the admixture with such incoming gas ofabout four to five volumes of reaction product gases will generally befound suillcient to preheat the fresh incoming gas to reactivetemperatures and at the same time provide for adequate temperaturecontrol in the reaction chamber. Where such quantities of products fromthe converter are introduced into the incoming gases, the resulting gasmixture in pipe 50 maycontain for example by volume 15.0% S02, 9.0% CH4,22.0% C02, 3.0% Hrs, 16.0% S2, and balance water vapor. It will beunderstood that if the temperature of the product gas leaving thereaction chamber through the outlet pipe 60 should rise substantiallyabove 625 C. it is only necessary to adjust the valve 82 so as to permitrecirculation of larger quantities of reacted gases through theconverter.

The gaseous products of the reaction, discharged from the apparatusthrough the outlet pipe 60, and containing for example by volume 26.0%00:, 3.5% S02, 3.5% HrS, 20.0% S2, 2.3% CH4, and about 44.0% H20, arepassed through any suitable cooler or condenser to efliect condensationof sulfur vapor and recovery of sulfur. Should the gases leaving thecondenser contain appreciable quantities of sulfur dioxide and hydrogensulfide. the tail gases of the condenser may, after adjustment of thegas mixture to provide therein reacting proportions of sulfur dioxideand hydrogen sulfide, be passed through a second body of catalyst, suchas bauxite, to recover the sulfur.

From the foregoing it will be observed that the present inventionprovides a process whereby the sulfur dioxide content of relativelyconcentrated sulfur dioxide gas mixtures can be economically reduced toelemental sulfur by reaction with reducing agent in the presence of acatalyst. The invention further provides for adequate temperaturecontrol by diluting the gas stream passing through the converter. Byeffecting this dilution of the gas stream with reaction products,important operating advantages are obtained.

The reaction products are largely inert with respect to the reactiontaking place in the converter, and thus provide for adequate temperaturecontrol therein. The reaction products contain relatively large amountsof sulfur, and hence when recycled and utilized for temperature controldo not effect reduction of the sulfur content of the products dischargedfrom the apparatus through pipe 80, as would be the case in the eventthat gases other than the reduction products were employed as dilutingmedium. A high sulfur content in the fully converted gases makesultimate recovery of sulfur more simple and economical because of thesmaller volume of gas to handle.

Because'of the particular arrangement of the packing in the converter,dilution of a concentrated gas mixture is made possible, and largevolumes of reacting gases may be passed through the converter andintimately contacted therein with large surfaces of catalytic materialwithout causing undue resistance to gas flow through the converter.Additionally, the process is such that ilnely divided catalytic materialwhich may be carried through and out of the reaction chamber by .gascurrents may be readily replaced by catalyst fed into the converter forthis purpose formed catalysts.

through inlet 3|, thus maintaining the catalyst body in the form of aplurality of suspended mounds of finely divided catalytic material.

A-further important aspect of the invention is the provision of a methodin which finely divided catalytic material may be economically utilized,thus avoiding expensivepreparation of specially This feature of theimproved method is particularly advantageous since bauxite fines may beemployed, thus rendering readily available for use large quantities ofbauxite which may not be utilized as catalysts without pelleting orother preparation. The invention alsoovercomes the disadvantages-arisingfrom the use of beds of bauxite in lump form. In such instances, thelumps disintegrate, and gradually increase resistance to gas passagethrough the catalytic body. Further, by employing bailies the upperportion of the preferred temperature range, say, at temperatures aboveabout 550 C. The present method is not limited, however, to the use ofbauxite, since other catalysts such as iron oxide, pyrites cinder,tantalum .oxide, aluminum oxide, and others may be employed.

It is also to be noted that the invention is not restricted to thereduction of sulfur dioxide to produce elemental sulfur and/or hydrogensulfide. The process may be employed to effect other catalyticreactions, for example, oxidation of sulfur dioxide to sulfur trioxide.In such operations, the baffles of bauxite or other suitable 85refractory material may be impregnated with a suitable catalyst such asvanadium or platinum, and if desired further reaction may be broughtabout in the presence of platinum, vanadium or other catalyst in finelydivided form, fed into the converter as already described in connectionwith the preferred embodiment of the invention.

In situations where operations are such that the gas stream, afteradmixture of reducing gases at inlet 51, may already be heated toapproximately reactive temperatures, no further preheating of the'g'asstream is required, and the hot reaction products, which are to berecycled through the converter to control the temperature therein, maybe cooled as required by means of a cooler, not shown, and then admitteddirectly into the converter. Further, reducing agents -other thannatural gas may be employed, and may be introduced into the converterwithout previous admixture with the incoming sulfur dioxide gas stream.

In the foregoing description and in the subtended cla ms, the termfinely divided is intended to include granular material of anyconvenient size not too large to interfere with free passage of suchmaterial through the checkerwork.

I claim:

1. The method of reducing sulfur dioxide contained in a concentratedsulfur dioxide gas mixture which comprises diluting the gas mixture withinert gases whereby the volume of. the gas mixture is increased,introducing the gas mixture and reducing agent into a reaction zone,maintaining in the reaction zone a checkerwork supporting finelydivided, loosely associated catalytic material, and reacting sulfurdioxide and reducing agent while passing the same through thecheckerwork.

2. Apparatus of the character described comprising a reaction chamber,means for passing reactant materials through the reaction chamber, meansfor forming and maintaining in the reaction chamber a plurality ofsuspended mounds of catalytic material, mounds of catalytic materialsupported by said second mentioned means, and means for replenishing themounds ,means for forming and maintaining in the reaction chamber acatalyst body comprising checkerwork supporting mounds of looselyassociated catalytic material whereby resistance to gas flow through thereaction chamber is reduced, means for withdrawing reaction productsfrom the exit gas stream of the reaction chamber, and means for mixingsuch products with the reactant gas mixture entering the reactionchamber.

4. Apparatus of the character described comprising a reaction chamber,means for introducing finely divided catalytic material and reactantmaterials into the reaction chamber, means for effecting contact ofreactant materials and catalytic material comprising a plurality ofhorizontal, superposed series of elongated baiiles, the bailies of eachseries being spaced apart a distance less than the width of the bailles,the baflles of each series being angularly arranged with respect to thebattles of a contiguous series, the baflles of alternate series beingdisposed in parallel and vertically staggered relation, whereby aplurality of circuitous passages through the checkerwork are formed,mounds of loosely associated catalytic material on said bailies, meansfor withdrawing reaction products from the reactionchamber, and meansfor admixing portions of the reaction products with reactant materialsentering the reaction chamber.

5. The method of conducting catalytic reactions which comprisesintroducing reactant substances into a reaction zone, and reacting thesubstances in the reaction zone by passing said substances through acheckerwork supporting spaced apart mounds of. loosely associatedcatalytic material while causing at least a sub stantial portion of saidsubstances to impinge upon the surfaces of said mounds in directionssubstantially normal to said surfaces.

6.'The method of conducting catalytic reactions whichcomprises'introdu-cing reactant substances into a reaction zone, andreacting the substances in the reaction zone by passing saidsubstanccsg' through a checkerwork supporting spaced apart mounds ofloosely associated bauxite while causing at least a substantial portionof said substances to impinge upon the surfaces of said mounds indirections substantially normal to said surfaces.

7. The method of reducing sulfur dioxide which comprises introducingsulfur dioxide into a reaction zone, and causing reduction of the sulfurdioxide in the said zone by passing the sulfur dioxide throughcheckerwork supporting spaced apart mounds of loosely associatedmaterial aiding in the reduction while causing at least asubstantial'portion of reacting substances to impinge upon the surfacesof said mounts in directions substantially normal to said surfaces.

8. The method of reducing sulfur dioxide which comprises introducingsulfur dioxide and reducing agent into a reaction zone, maintaining inthe tion reaction not substantially in excess of about reaction zone a.catalyst body comprising checkerwork supporting mounds of looselyassociated catalytic material, reacting the sulfur dioxide and reducingagent while passing the same in dioxide gas mixture is produced,diluting the gas mixture with inert gas in amount sufllcient to maintainthe temperature of a subsequent reduc- 650 (2., maintaining in areaction zone a catalyst body comprising a refractory checkerwork supporting loosely associated finely divided bauxite,

directions substantially normal to said surfaces.

HENRY F. MERRIAM.

CERTIFICATE or CORRECTION.

5 contact with the catalytic material and causing introducing the gasmixture and reducing agent 5 at least a substantial portion of reactingsubinto the reaction zone,reac ting sulfur dioxide and stances toimpinge upon the surface ,of said reducing agent while passing the samein contact mounds in a direction substantially normal to with thebauxite and causing at least a substantial said surfaces. portion of thereacting substances to impinge 1 0 9. The method of recovering sulfurvalues from upon the surfaces of said mounds in directions i0 sulfuricacid sludgewhich comprises decomposing substantially normal to saidsurfaces, and recovsludge to form a sulfur dioxide gas mixture,coolering sulfur from the reaction products. ing the gas mixture toremove therefrom conden- 11. Apparatus of the character. describedcomsable substances whereby the sulfur dioxide conprising a reactionchamber, means for maintaintent of the gas mixture is increased and arelaing in the reaction chamber a plurality of spaced l5 tlvelyconcentrated sulfur dioxide gas mixture apart bodies of finely divided,loosely associated produced, diluting the gas mixture withinertcatalytic material, bodies of loosely associated gas in amountsufficient to maintain the tempercatalytic material supported by saidmeans, and

ature of a subsequent reduction reaction not in means for passingreactant materials through the excess of optimum reduction temperaturewherereaction chamber in a direction to cause at least 20 by the volumeof the gas mixture is increased, a substantial portion of said reactantmaterials maintaining in a reaction zone a catalyst body to impinge uponthe surfaces of said bodies of comprising checkerwork supporting spacedapart catalytic material in a direction substantially mounds of looselyassociated, finely divided catanormal to said surfaces.

lytic material, introducing the gas mixture and 12. The method ofreducing sulfur dioxide con- 25 reducing agent into the reaction zone,reacting tained in a concentrated sulfur dioxide gas mixsulfur dioxideand reducing agent while passing ture which comprises adding to the gasmixture the same in contact with the catalytic material inert gas inquantity sufficient to dilute the reand causing at least a substantialportion of the actant gas mixture to such extent that til: temreactingsubstances to impinge upon the surfaces perature of the subsequentreduction reaction 30 of said mounds in a direction substantially normaldoes not exceed optimum reduction temperature, to said surfaces, andrecovering sulfur from the whereby the volume of the reactant gasmixture is reaction products. increased, introducing the gas mixture andreduc- 10. The method of recovering sulfur values ing agent into areaction zone, and reacting the from sulfuric acid sludge whichcomprises desulfur dioxide and reducing agent therein by 35 composingsludge to 'form a sulfur dioxide gaspassing the same through checkerworksupportmlxture, cooling the gas mixture to remove ing spaced apartsuspended mounds of loosely therefrom condensable substances whereby theassociated catalytic material while causing at sulfur dioxide content ofthe gas mixture is inleast a substantial portion of said substances to p0 creased and a relatively concentrated sulfur impinge upon the surfacesof said mounds in 40 August 17, 1937.

Patent No. 2,090,217.

HENRY F. MERRIAM.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 4,second column, line 3, claim 2, before "suspended" insert the wordsspaced apart; and that the said Letters Patent should be read with thiscorrection therein that the same may conform to the record of the casein the Patent Office.

- sighed and sealed this 5th day of October, A. o. es r.

Henry Van Arsdale Acting Commissionenof Patents.

(Seal) tion reaction not substantially in excess of about reaction zonea. catalyst body comprising checkerwork supporting mounds of looselyassociated catalytic material, reacting the sulfur dioxide and reducingagent while passing the same in dioxide gas mixture is produced,diluting the gas mixture with inert gas in amount sufllcient to maintainthe temperature of a subsequent reduc- 650 (2., maintaining in areaction zone a catalyst body comprising a refractory checkerwork supporting loosely associated finely divided bauxite,

directions substantially normal to said surfaces.

HENRY F. MERRIAM.

CERTIFICATE or CORRECTION.

5 contact with the catalytic material and causing introducing the gasmixture and reducing agent 5 at least a substantial portion of reactingsubinto the reaction zone,reac ting sulfur dioxide and stances toimpinge upon the surface ,of said reducing agent while passing the samein contact mounds in a direction substantially normal to with thebauxite and causing at least a substantial said surfaces. portion of thereacting substances to impinge 1 0 9. The method of recovering sulfurvalues from upon the surfaces of said mounds in directions i0 sulfuricacid sludgewhich comprises decomposing substantially normal to saidsurfaces, and recovsludge to form a sulfur dioxide gas mixture,coolering sulfur from the reaction products. ing the gas mixture toremove therefrom conden- 11. Apparatus of the character. describedcomsable substances whereby the sulfur dioxide conprising a reactionchamber, means for maintaintent of the gas mixture is increased and arelaing in the reaction chamber a plurality of spaced l5 tlvelyconcentrated sulfur dioxide gas mixture apart bodies of finely divided,loosely associated produced, diluting the gas mixture withinertcatalytic material, bodies of loosely associated gas in amountsufficient to maintain the tempercatalytic material supported by saidmeans, and

ature of a subsequent reduction reaction not in means for passingreactant materials through the excess of optimum reduction temperaturewherereaction chamber in a direction to cause at least 20 by the volumeof the gas mixture is increased, a substantial portion of said reactantmaterials maintaining in a reaction zone a catalyst body to impinge uponthe surfaces of said bodies of comprising checkerwork supporting spacedapart catalytic material in a direction substantially mounds of looselyassociated, finely divided catanormal to said surfaces.

lytic material, introducing the gas mixture and 12. The method ofreducing sulfur dioxide con- 25 reducing agent into the reaction zone,reacting tained in a concentrated sulfur dioxide gas mixsulfur dioxideand reducing agent while passing ture which comprises adding to the gasmixture the same in contact with the catalytic material inert gas inquantity sufficient to dilute the reand causing at least a substantialportion of the actant gas mixture to such extent that til: temreactingsubstances to impinge upon the surfaces perature of the subsequentreduction reaction 30 of said mounds in a direction substantially normaldoes not exceed optimum reduction temperature, to said surfaces, andrecovering sulfur from the whereby the volume of the reactant gasmixture is reaction products. increased, introducing the gas mixture andreduc- 10. The method of recovering sulfur values ing agent into areaction zone, and reacting the from sulfuric acid sludge whichcomprises desulfur dioxide and reducing agent therein by 35 composingsludge to 'form a sulfur dioxide gaspassing the same through checkerworksupportmlxture, cooling the gas mixture to remove ing spaced apartsuspended mounds of loosely therefrom condensable substances whereby theassociated catalytic material while causing at sulfur dioxide content ofthe gas mixture is inleast a substantial portion of said substances to p0 creased and a relatively concentrated sulfur impinge upon the surfacesof said mounds in 40 August 17, 1937.

Patent No. 2,090,217.

HENRY F. MERRIAM.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 4,second column, line 3, claim 2, before "suspended" insert the wordsspaced apart; and that the said Letters Patent should be read with thiscorrection therein that the same may conform to the record of the casein the Patent Office.

- sighed and sealed this 5th day of October, A. o. es r.

Henry Van Arsdale Acting Commissionenof Patents.

(Seal)

